How child porn killed my app called YayNay
medium.com
medium.com
Any system that does not fight spam will quickly become only spam (porn considered as spam in this case as it's not the point of the app). Any image rating/manipulation program will quickly become only spam and porn unless heavily moderated.
TL;DR: If you aren't considering spam and security issues when developing apps please stop. Either read up, in detail, on how to do it correctly or add a developer that understands the issue.
Just 1? Wow, you gave up way too easily.